You may have a design flaw in your system. If it is a closed system your PRV should be the fill valve and it would be set at about 15 psi. The water does NOT FLOW through it. If it is an open system using the domestic water heater, you would have to give a drawing of how you handle the connections at both ends to keep the reduced pressure. And if you are reducing the pressure into the water heater, it would increase every time you open both hot and cold water valves at the same faucet. But even then the water would not flow through the valve into the grid, unless you have some "innovative" way of piping it.